In the past, information communication between processor-based systems, such as local area networks (LAN) and other general purpose computers, separated by significant physical distances has been an obstacle to integration of such systems. The choices available to bridge the physical gap between such systems have not only been limited, but have required undesirable tradeoffs in cost, performance, and reliability.
One group of historically available communication choices includes such solutions as the utilization of a standard public switch telephone network (PSTN) or multiplexing signals over an existing physical link to bridge the gap and provide information communication between the systems. Although such solutions are typically inexpensive to implement, they include numerous undesirable traits. Specifically, since these existing links are typically not designed for high speed data communication, they lack the bandwidth through which to communicate large amounts of data rapidly. As in-building LAN speeds increase to 100 Mbps, the local PSTN voice grade circuits even more markedly represent a choke point for broadband metropolitan area access and therefore are becoming a less and less desirable alternative. Furthermore, such connections lack the fault tolerance or reliability found in systems designed for reliable transmission of important processor-based system information.
Another historically available group of communication choices is found at the opposite end of the price spectrum than those mentioned above. This group includes such solutions as the utilization of a fiber optic ring or point-to-point microwave communication. These solutions are typically cost prohibitive for all but the larger users. The point-to-point systems require a dedicated system at each end of the communication link which lacks the ability to spread the cost of such systems over a plurality of users. Even if these systems were modifiable to be point-to-multipoint, to realize the economy of multiple system use of some system elements, the present point-to-point microwave systems would not provide broadband data services but rather traditional bearer services such as T1 and DS3. Furthermore these systems typically provide a proprietary interface and therefore do not lend themselves to simple interfacing with a variety of general purpose processor-based systems.
Although a fiber optic ring provides economy if utilized by a plurality of systems, it must be physically coupled to such systems. As the cost of purchasing, placing, and maintaining such a ring is great, even the economy of multi-system utilization generally does not overcome the prohibitive cost of implementation.
Accordingly, point-to-multipoint systems such as shown and described in above referenced U.S. Pat. No. 6,016,313, entitled “System and Method for Broadband Millimeter Wave Data Communication,” have been developed to provide broadband communication infrastructure in an efficient and economical alternative. For example, a preferred embodiment point-to-multipoint system described in the U.S. Pat. No. 6,016,313 provides for a network of point to multipoint hubs to establish cellular type coverage of a metropolitan area. Such systems are generally more economical to deploy than systems such as fiber optic networks, due to their use of wireless links avoiding the cost of laying fiber to all nodes on the network, and point-to-point microwave, due to the sharing of resources among several or many users.
It is generally desirable for systems providing broadband data services to do so with a high level of reliability. For example, the fact that such a broadband communication system is adapted to carry data quickly suggests that a large volume of data is carried there through. However, systems such as the above referenced point-to-multipoint system may present a single point of failure, such as an antenna, a radio, or a modem, which may affect communications with respect to a number of subscribers. Accordingly, it may be desirable to provide for redundancy for one or more components. However, any such redundancy is preferably carefully implemented in order that the desired economies leading to selection of such a system architecture are not negated.
Moreover, systems providing data communication, such as in a SONET optical network, are often required to provide very reliable and high quality communications, such as providing error free communication 99.999% of the time (often referred to as “five nines”). Accordingly, it may be desirable to adapt broadband communication systems such as the aforementioned point-to-multipoint wireless communication systems to provide the same or similar high quality, reliable, communications, such as where the wireless systems are utilized to provide a communication link with or within a system otherwise providing communication to such a standard.
A need therefore exists in the art for systems and methods for providing a high level of communication system reliability through the use of redundant components. A further need exists in the art for such systems and methods to be adapted such that they are deployed and operated economically and yet may be relied upon to provide a desired level of service and date throughput. A still further need exists in the art for such systems and methods to be implemented with optimization of available spectrum utilization.
The present invention is directed to a system and method which is adapted to provide communication link redundancy for a plurality of primary communication links using a common redundant configuration. For example, according to a preferred embodiment, a single redundant link portion of a system is deployed to provide redundancy for a number of primary link portions of the system. According to the preferred embodiment, this single redundant link portion of the system is configured to conduct communications substantially commensurate with any one of the primary link portions of the system for which it is providing redundancy. Such a configuration allows a single redundant system portion, which generally remains idle during proper operation of the primary link system portions, to be relied upon to provide backup communications for a number of primary link system portions. Accordingly, the complexity and cost of a redundant link portion of a system may be reduced while still providing adequate backup for any one of the primary link system portions' failure.
Although a preferred embodiment redundant link portion of the system is configured to provide communications commensurate with only one of the primary link portions at a time, such a configuration is expected to provide adequate redundancy due to the unlikelihood of simultaneous failure at multiple ones of the plurality of primary communication links for which redundancy is being provided. To further aid in such a configuration being relied upon to provide adequate redundancy, the preferred embodiment uses modular components and/or is otherwise adapted to facilitate rapid repair of failing primary communication links, thereby further decreasing the likelihood of simultaneous failure at multiple ones of the plurality of primary communication links. Moreover, even where multiple such failures are experienced, the preferred embodiment redundant link portion of the system is adapted to provide communications for all such failed primary links, albeit at a reduced capacity.
According to a most preferred embodiment, the communication system for which communication link redundancy is provided is a sectored wireless communication system. According to this most preferred embodiment, sectors of the wireless communication system may each provide at least one primary communication link. A redundant link portion of a system adapted according to the present invention may provide link redundancy for a plurality of sectors. In a preferred embodiment, the communication system provides wireless communication between different computer networks, where any one or all of the different computer networks may be any one of the following: a public switched telephone network, a private branch exchange, a router, the internet, a private network, or a single computer.
According to an embodiment of the present invention, the multiple primary sectors, for which common structure is relied upon to provide redundancy, utilize different channel sets such as frequency division multiple access (FDMA) channels, time division multiple access (TDMA) channels, code division multiple access (CDMA) channels, and/or the like. Preferably, the redundant link portion of a system adapted according to the present invention provide link redundancy throughout each such sector using a unique channel set assigned thereto (whether FDMA, TDMA, and/or CDMA) so as not to substantially interfere with communications in ones of the sectors when relied upon to provide communications for a failed one of the sectors. Accordingly, preferred embodiment subscriber units, or other systems utilizing the communication links, are channel (i.e., frequency, time, code) agile so as to allow their operation both on a primary link channel set and a redundant link channel set.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.